1. Field of the Invention
The present invention relates generally to a method and apparatus for increasing the efficiency of hydrocarbon combustion processes to thereby reduce the production of undesirable emissions. More particularly, the invention provides an apparatus and method for conveying, at a precisely controllable rate, minute quantities of a combustion enhancing substance directly to the site of combustion.
2. Description of the Prior Art
A wide variety of methods and devices have been disclosed that are intended to enhance the combustion of hydrocarbon fuels by introducing various substances into the combustion process. The intent is to improve efficiency, i.e. to increase the amount of the fuel's inherent chemical energy that is converted into thermal energy, and simultaneously to decrease undesirable emissions including unburned or incompletely burned hydrocarbons, carbon monoxide, and nitrogen oxides. Bringing about a more complete oxidation of the hydrocarbons and carbon monoxide has the simultaneous effect of increasing efficiency and decreasing the undesirable emissions.
A wide variety of substances have been relied upon to perform a variety of functions in the interests of enhancing combustion processes. Coreactants, catalysts, and as well as compounds subject to operating mechanisms not fully understood have been introduced into combustion processes via the fuel supply, the oxidant supply or into the fuel and oxidant comixture just prior to or during actual combustion.
The viability of a particular system depends not only on the efficacy of the substance utilized, but also on how easily the substance can be handled as well as how easily the substance can accurately be delivered into the combustion process in a highly dispersed form at the proper levels. Substances have been identified that are effective at ppb-range concentrations but systems attempting to deliver such small concentrations in highly dispersed form have suffered from complexity and fail to maintain proper concentration levels. Maintaining the proper concentration level is important not only in terms of the economic considerations involved, but also because the presence in the combustion process of too little as well as too much active substance may diminish its enhancing effect.
Platinum is an example of a substance known to promote combustion reactions at concentrations as low as 80 ppb of fuel. The extremely low concentration requirement precludes simply finely dividing the metal for gradual introduction into a combustion process not only in terms of actually being able to achieve 80 ppb, but also in terms of sufficiently dispersing such a small quantity of solid material amongst a typically highly dispersed fuel/oxidant combustible mixture. Platinum has extremely high melting and boiling points and therefore a commensurately low vapor pressure which hinders attempts to introduce the substance into a combustion process as a vapor. As a result of platinum's physical properties, direct addition of metallic platinum has not provided a viable approach to combustion enhancement. Various compounds of platinum have therefore been considered as vehicles for introducing a highly dispersed form of platinum into a combustion process, lots of attention having been focused on solutions of such compounds. While systems have been proposed that do thereby succeed in delivering the desired concentrations of highly dispersed platinum into a combustion process, practical problems prevail that make such systems complex and nonetheless unable to maintain a steady delivery rate. Moreover, the disclosed systems appear incapable of quickly and easily adjusting for changing feed rate requirements. A typical example of a prior art system is that provided by B. J. Robinson, in U.S. Pat. No. 4,295,816 wherein a system is described that introduces minute quantities of platinum into a diesel or gasoline engine's combustion chamber. A small quantity of combustion air is bubbled through a platinum compound containing aqueous solution at a constant rate to generate a catalyst containing mist which is then gradually drawn into the combustion chamber. This bursting bubble technique reportedly serves to draw out the catalytically active solute without significantly depleting the solvent, although some of the solvent is subject to evaporation. It would appear to be extremely difficult to maintain a constant platinum compound concentration within the aqueous solution which would have a commensurate effect on the amount of platinum transferred to the mist generated by the bubbling action. It is further conceivable that factors such as air temperature, solution temperature, and atmospheric pressure and humidity could effect the transfer rate of the platinum compound from solution to the mist. Less than the optimal catalyst concentration level would diminish the desired combustion enhancing effect, while greater than optimal concentrations would be wasteful and additionally, may in fact have a deleterious effect on the performance of the system as well. The inaccuracy of the delivery system as well as the problems attendant with the handling of solutions which require periodic concentration adjustment provides a typical example of the disadvantages associated with prior art systems. Similar systems have been proposed for a wide variety substances thought to have a combustion enhancing effect including rhenium compounds.
Additional considerations are of critical importance in automotive applications wherein the combustion enhancing substance must not only be consumed at an economical rate, but the bulk and weight of the substance must be such so as to provide reasonably long replenishment intervals. Further, the combustion enhancing substance handling and delivery system should be adaptable to existing engine and vehicular designs. In the case of aftermarket applications, the system must further be readily adaptable to particular vehicles already in service.
The prior art has failed to provide a hydrocarbon combustion enhancing system capable of delivering minute quantities of an easily handleable and effective combustion enhancing substance at a precisely controllable rate for extended periods of time in an economical fashion. Moreover, systems have not been disclosed that provide for extended service cycles and which are readily adaptable to existing combustion processes.